Interconnection and matching of an RF excited gas laser to an RF generator is typically accomplished by the use of a 50 ohm coaxial transmission line with separate matching networks at both ends. The matching network at the laser end usually steps up the line impedance to a range between several hundred and several thousand ohms, while the matching network at the RF generator end steps the line impedance down to the low values required for the generator's transistor output stage. Other functions of the matching networks are to account for the two different impedance values of the plasma tube, before and after breakdown. Yet another function of the matching network is to cancel reactive components at source and load. U.S. Pat. No. 4,455,658 by Sutter, U.S. Pat. No. 4,169,251 by Laakmann and U.S. Pat. No. 4,363,126 by Chenausky et al. are typical examples of such interconnect systems.
An exception to these standard techniques is taught by Laakmann in U.S. Pat. No. 4,837,772. In this disclosure a lumped constant matching system is used directly between the RF generator's output stage transistors and the laser. No interconnect cables are used, for reasons disclosed there. However, the main feature of that disclosure is the "self-oscillating technique" that eliminated much of the complexity of matching drive frequency and laser as well as accounting for the two different impedance states of the plasma contained within the laser's plasma tube.
In U.S. Pat. No. 4,373,202 by Laakmann, et al., the technique is disclosed of using a 75 ohm quarter wave transmission line within a 50 ohm system to automatically adjust power in order to decrease "hot spots" within the plasma tube and provide a more stable discharge. However, both laser and power source are still matched to 50 ohm impedances and produce sinusoidal waveforms.